Grinding machine



p 1942- w. H. WOOD 2,294,872

GRINDING MACHINE I Filed Oct. 26, 1940 4 Sheets-Sheet l (is IOZ awe/who's 85 \A/HL L H55 H W000 WQ. eaxm Sept. 1, 1942.

w. H. WOOD 2,294,872 GRINDING- MACHINE Filed Oct. 26, 1940 4 Sheets-Sheet 2 gwm R WELL/7:5 f7! W000 MUM p 1942- w. H. w ooD 2,294,872

GRINDING MACHINE Filed 001;. 26, 1940 4 Sheets-Sheet 3 wmeaueam Guam,-

Patented Sept. 1, 1942 UNHTED STATES PATENT OFFICE GRINDING MACHINE Wallace H. Wood, Worcester, Mass, assignor to Norton Company, Worcester, Mass., a corporation of Massachusetts Application October 26, 1940, Serial No. 362,898

7 Claims.

The invention relates to grinding machines, and more particularly to a hydraulically operated grinding wheel feeding mechanism.

One object of the invention is to provide a simple and thoroughly practical hydraulically operated cylindrical grinding machine. Another object of the invention is to provide a hydraulically operated grinding wheel feeding mechanism. A further object of the invention is to provide a hydraulically operated single vane type motor driven wheel feeding mechanism. A further object of the invention is to provide a control mechanism for a hydraulic motor wheel feeding mechanism which may be actuated continuously for a plunge-cut operation or intermittently in timed relation with the table reciprocating movement for a traverse grinding operation.

A further object of the invention is to provide a combined selector and speed control valve for a hydraulic feed motor whereby the motor may be actuated either continuously or intermittently and whereby the speed of the motor may be varied either during continuous or intermittent operation. A furtherobject of the invention is to provide a hydraulically operated wheel feeding mechanism including a vane type fluid motor which may be controlled by one of two difierent control valves which may be selected by means of a manually operable selector valve whereby either a continuous feed may be obtained for a plunge-cut grinding operation or an intermittent feed at the ends of the table stroke for a traverse grinding operation may be readily obtained.

Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts, as will be exemplified in the structure to be hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the drawings, in which is shown one of various possible embodiments of th mechanical features of this invention,

Fig. l is a front elevation of the improved grinding machine;

Fig. 2 is a cross-sectional view through the grinding machine wheel feeding mechanism, showing the wheel slide and headstock in elevation;

Fig. 3 is a diagrammatic view, showing the hydraulic wheel feed control mechanism together with the piping arrangement;

Fig. 4 is a vertical sectional view, on an enlarged scale, through the fluid motor for actuating the wheel feed and also through the control valve mechanism therefor; I

Fig. 5 is a cross-sectional view, taken approximately on the line 55 of Fig. 4;

Fig. 6 is a sectional view, taken approximately on the line 6-6 of Fig. 4; and

Fig. '7 is a diagrammatic view, taken approximately on the line 1-7 of Fig. 4.

A grinding machine embodying this invention has been illustrated in the drawings, comprising a base H) which supports a longitudinally movable work supporting table II on a V-way I2 and a flat way l3 for a longitudinal reciprocatory movement relative to the base 19. A headstock M and a footstock I5 are mounted on the table H and are arranged rotatably to support a cylindrical work piece It in operative relation with a rotatable grinding wheel IT. The grinding wheel ll is'rotatably supported on a transversely movable wheel slide of the usual and well known type, such as that shown in the expired U. S. patent to Norton, No. 762,838 dated June 14, .1904. In the preferred form, an electric motor 2!] is mounted on the wheel slide 18. The motor 26 is provided with a pulley 2| which is connected by a driving belt 22 with a pulley 23 mounted on the end of a wheel spindle 24. The wheel spindle 24 serves as a support for the rotatable grinding wheel 11.

A fluid pressure mechanism may be provided for reciprocating the work table II. As illustrated in the drawings, a cylinder 39 is fixedly mounted to the underside of the table H. The cylinder contains a piston (not shown) which is connected by apair of hollow piston rods 32 and 33 with a pair of hollow brackets 34 and 35 which are fixedly mounted on opposite ends of the base l0.

In the preferred construction the base II] is formed as a hollow box-like construction in which the lower portion serves as a reservoir 38. Fluid is drawn from the reservoir 38 through a pipe 39 by means of a motor driven fluid pump 40 and is forced through a pipe 4! to a table control valve 42. A fluid pressure relief valve 43 is provided in the pipe 4| so as to allow excess fluid under pressure within the system to return directly to the reservoir 38, thus'maintaining a desired and predetermined pressure within the fluid system. The details of construction of the table control valve 42 together with the connections to the cylinder 30 have not been illustrated in detail in the present application since they are not considered to be a part of the present invention,

The table reciprocating mechanism is substantially identical with that shown in my prior U. S. Patent No. 2,071,677 dated February 23, 1937, to which reference may be had for details of disclosure not contained herein.

A manually operable control lever 44 is provided for actuating the control valve 42. The lever 44 serves, as in my prior patent, to actuate a stop and start valve (not shown) and by rotation of the knob 45, the normal speed of the table Il may be readily controlled as desired. The control valve unit 42 also contains a reversing valve which is arranged to be actuated automatically by means of a table reversing lever 46. The lever 46 is pivotally supported on a stud 41 on the base ID of the machine. A pair of adjustable table dogs 48 and 49 are adjustably supported in a T-slot 50 formed in the front edge of the table II. The dogs 48 and 49 are arranged successively to engage and shift the reversing lever 46 so as to control the length of the reciprocatory stroke of the table II.

The table II may be traversed longitudinally by means of a manually operable traverse wheel when desired. The manually operable traversing mechanism has not been illustrated in detail herein since it is not considered to be a part of the present invention. The table traversing mechanism is identical with that shown in my prior U. S. Patent No. 2,071,677 above referred to, to which reference may be had for details of disclosure not contained herein.

A wheel feeding mechanism is provided for feeding the wheel slide [8 together with the grinding wheel I! transversely relative to the base on the usual V-way and flat way (not shown). A depending half nut 55 depends from the under side of the wheel slide 18. The half nut 55 meshes with or engages a rotatable cross feed screw 56 which is rotatably journalled in bearings 51 and 58. The bearings 51 and 58 are mounted in fixed relation with the base ID. The left-hand end of the feed screw 56 is slidably keyed within a sleeve 59 which is in turn fixedly mounted on a shaft 69. The left-hand end of the shaft 60 is journalled in a bearing 6|. A gear 62 is mounted on the outer end of the shaft 60 and meshes with a pinion 63 formed on the inner end of a sleeve 64. The sleeve 64 is rotatably supported on a fixed stud 65 which is mounted in fixed relation with the base ID of the machine. A ratchet wheel 66 is formed integral with the sleeve 64. A manually operable hand wheel 61 is also rotatably supported on the stud 65 and is drivingly connected to rotate the sleeve 64 when desired.

It will be readily apparent from the foregoing disclosure that when the manually operable feed wheel 61 is rotated, a rotary motion will be imparted through the sleeve 64, the pinion 63, the gear 62, the shaft 6|], the sleeve 59, to rotate the feed screw 56 which in turn transmits a transversemovement through the half nut 55 to the wheel slide l8 and grinding wheel 17. The direction of rotation of the manually operable feed wheel 61 determines the direction of'rotation of the feed screw 56 and also the direction of transverse movement of the wheel slide l8 and the grinding wheel 17,

In order to feed the grinding wheel transversely for a grinding operation, it is desirable to provide a power actuated feed which may be either operated continuously for a plunge-cut grinding operation or may be actuated intermittently and automatically at the ends of the tent.

work table stroke for a traverse grinding operation.

An oscillatable arm 68 is rotatably supported on the periphery of the sleeve 64. The arm 68 serves as a support for a feed pawl 69 which is pivotally supported by a stud 10 to the arm 68. It will be readily apparent from the foregoing disclosure that if the arm 68 is oscillated, the ratchet pawl 69 engaging the teeth of the ratchet wheel 66 will rotate the feed screw and thereby impart a transverse feeding movement to the grinding wheel slide I8 and the grinding wheel I! to feed it toward the work axis to grind the work piece to the desired and predetermined ex- The oscillatable arm 68 is connected by means of a stud H to the upper end of a link 12. An adjustable rotatable crank plate 73 is fixedly supported on a shaft 74. The crank plate 13 is provided with a radially extending T-shaped slot 15 in which fits the head 16 of a bolt 71. The bolt 11 in turn supports a sleeve 78. The outer end of the bolt 18 is provided with a screw thread 79 on which fits a manually adjustable nut 80. The periphery of the sleeve 18 fits within a bearing surface 8| formed in the lower end of the link 12. In the position of the parts as shown in Fig. 4, it will be readily apparent that if the shaft 74 is oscillated, a rotary motion will be imparted to the crank plate 13 to impart a crank motion to the bolt 11 and the sleeve 18 which in turn transmits a vertical motion to the link 12, thereby oscillating'the pawl supporting arm 68 to produce a desired and predetermined feeding movement of the wheel slide I8 and the grinding wheel [7.

The extent of oscillation of the feed pawl 69 may be readily varied by adjusting the eccentricity of the bolt 17 and sleeve I8. As shown in Fig. 4, the bolt and sleeve 18 are positioned to impart a maximum oscillatory stroke through the link 12 to the pawl carrying arm 68. If it is desired to decrease the amount of feeding movement imparted for each actuation of the crank plate 63, the nut is loosened and the bolt I! together with the sleeve 18 is moved upwardly so that the bolt head 76 moves upwardly within the T-slot 15 (Fig. 4). During this movement the axis of the bolt 1'! and sleeve 78 approaches the axis of the shaft 74.

The axis of the bolt 77 and sleeve 18 is moved into a position to coincide with the axis of the shaft 14; then no oscillatory movement will be imparted to the feed pawl 69. It will be readily apparent that the extent of feed from the maximum, as shown in Fig. 4, to the minimum may be obtained by adjusting the position of the bolt 11, after which it may be readily locked in adjusted position by tightening the clamping nut 80.

It is desirable to provide a power actuated mechanism for oscillating the crank plate 13 either continuously for providing a plunge-cut feed during a plunge-cut grinding operation or intermittently in timed relation with the reciprocation of the work table H so that the wheel may be fed at the ends of the table stroke during a traverse grinding operation.

In the preferred construction, a fluid pressure mechanism is provided for actuating the feeding mechanism, comprising a fluid motor which is preferably of a single vane type having a circular chamber 86. A rotor 8'! is provided within the chamber 86. The rotor 87 is preferably formed as an integral part of the shaft 14. The rotor shaft 74 is rotatably supported in bearings 88, 89

and 90 formed in the casing 9| A single vane 32- is fixedly mounted on the rotor 81 and is arranged to travel through an arcuate path of approximately 270 degrees as fluid under pressure is admitted either to one side or the other thereof. A bafiie plate 93 is fixedly mounted within the chamber 86 and serves to form two motor chambers, namely, the motor chamber 86 and a motor chamber 04 on the other side of the vane 92. The motor 85 is connected by pipes or passages 95 and 95 with a reversing valve 9?. The reversing valve 91 is a shuttle type valve comprising a plurality of valve pistons 98, 99 and I00. The reversing valve 97 is provided with end chambers IOI and I02 so that it may be readily shifted from one end to the other by means of fluid under pressure.

The vane 92 of the fluid motor 35 (Fig. 5) is shown at the end of its circular path of movement in a clockwise direction. The vane 92 in Fig. 4 is shown in a midway position. In Figs. 3 and '7 the vane 92 is shown as approaching the end of its stroke in a counterclockwise direction, that is, with the fluid pressure passing into the motor chamber 94.

In the position of the parts as shown in Fig. 3, fluid under pressure from the motor-driven pump 48 passes through a pipe I03to a selector and speed control valve Iii-4. This valve I04 has been shown diagrammatically in Fig. 3 as comprising three sectional portions I05, lIl la and I041) to show clearly the passages and ports contained therein. The valve led is a rotary type selector valve, the function of which will be further described hereinafter. This valve comprises a valve rotor I535. The valve rotor IE5 is arranged so that fluid under pressure passing through the pipe I03 may pass through the passage I06 and through a pipe III] and a pipe I03 into a valve chamber I03 located between the valve pistons 93 and 99 and through the passage 95 into the fluid motor chamber 94 to move the vane 92 in a counterclockwise direction.

In order automatically to control the reversing valve for providing a continuous infeeding movement for a plunge-cut grinding operation, a pilot valve H is provided; or for providing an intermittent operation of the fluid motor in timed relation with the table movement, a pilot valve I II is provided. The pilot valve I50 is a piston type valve comprising valve pistons H2, II 3 and H4 forming valve chambers H and III; therebetween. The valve Iii! is operatively connected so that it may be shifted by and in timed relation with the rotary movement of the fluid motor vane 92.

A downwardly extending arm II! is fixedly mounted on a slide bar I I8 which is supported in guides I I3 and I formed in the motor and valve casing. The opposite ends of the slide rod -I I8 are connected by arms I2I and I 22 with the valve pistons H4 and I I2, respectively. The downwardly extending arm II! is arranged in the path of a pair of V-shaped arms I23 and I24 which are fixedly mounted on the motor shaft I4. The arms I23 and I24 are provided with actuating screws I25 and I28, respectively, which are arranged to engage the downwardly extending arm III of the valve H0 so as to shift the valve first in one direction and then in the other to control the admission of fluid under pressure to the opposite end chambers IIII and I02 of the reversing valve, thus automatically and continu ously causing an oscillatory movement of the motor vane 92 to be imparted to the feed pawl 69 to 75 provide a plunge-cut feeding movement of the grinding wheel I1. In th position as shown in Fig. 3, fluid under pressure in the pipe I01 passes through a pipe I28 to the valve chamber '5 of the valve H0 and passes out through a pipe I29 and through a valve chamber I30 in the valve I04. From the valve chamber I30 fluid passes through a pipe or passage I3I into the end chamber I III of the reversing valve 91 to move the reversing valve into its extreme right-hand end position (Fig. 3).

During the movement of the reversing valve toward the right, fluid may exhaust from the reversing valve end chamber I02 through a pipe I32, through a valve chamber I33 in the valve I04, and out through a pipe I34, through the valve chamber II6 of the pilot valve H0, and out through an exhaust pip I35 which returns exhaust fluid to the reservoir 38. It will be readily apparent from the foregoing disclosure that when the valve I04 is in the position illustrated in Fig. 3, the pilot valve III) will be rendered operative so that movement of the rotary vane 92 of the motor 85 will control the movement of the pilot valve III so as to provide a continuous oscillating movement of the fluid motor vane 92 which is in turn imparted t produce a continuous oscillation of the feed pawl I59, thereby producing a plunge-cut infeeding movement of the grinding wheel II.

The pilot valve III is also a piston type valve comprising valve pistons I 38, I39 and I40 which are arranged to form valve chambers MI and I 42. The valve III is provided with a valve stem I43 which is connected by a stud I44 with one end of a link I45. The other end of the link I45 is pivotally connected to a downwardly extending arm I45 (Fig. 1) which is operatively connected to move with the reversing lever 46.

It will be readily apparent from the foregoing disclosure that each time the reversing lever 45 is actuated by the table dogs 13 and as, a shifting movement will be imparted through the link I45 to shift the pilot valve III.

When it is desired to provide a traverse grinding feed, that is, an intermittent infeeding of the grinding wheel II at the ends of the reciprocatory stroke of the table II, the valve rotor I05 is rotated ninety degrees (Fig. 3), in which position fluid under pressure from the pipe I03 passes through the passage IOIia and through the pipe I238 to the reversing valve SI. In this position of the selector valve I2 4, fluid under pressure passing through the pipe I31 passes through a pipe I50, into the valve chamber I4I of the valve III, and passes out through a pipe I5I and through the valve chamber I30, and out through the pipe I3I into the end chamber IOI of the reversing valve 97 to move the valve pistons 98, 93 and I 00 toward the right (Fig. 3). During this movement, fluid under pressure with in the chamber I 02 is exhausted through the pipe I32, through the valve chamber I33 in the valve I04, out through a pipe I52, into the valve chamber I 42 of the valve III, and out through an exhaust pipe I53 which connects with the exhaust pipe I55 to convey exhaust fluid to the reservoir 38;

Similarly, when the reversing lever 46 is engaged by the table dog 48 to shift the reversing lever 45 in a clockwise direction, the valve pis tons I38, I39 and MI! of the valve III are shifted into their extreme left-hand position so that fluid under pressure within the pipe I50 enters the valve chamber I42 in the valve III and passes through the pipe I52, through the valve chamber I33, the pipe I32, into the end chamber I02 of the reversing valve 91 to move the valve pistons 98, 99 and I toward the left (Fig. 3), which movement shifts the valve into a reverse position. In the left-hand end position of the valve 91, fluid under pressure passing through the pipe I08 enters the valve chamber I09a located between the valve pistons 99 and I00 and passes outwardly through the passage 96 into the fluid motor chamber 86 to impart a clockwise movement to the motor vane 92, which movement is imparted through the crank plate I3 above described to impart an oscillatory movement to the feed pawl 69. During the clockwise movement of the vane 92, fluid is exhausted from the motor chamber 94, through the passage 95, and out through an exhaust pipe I54 which connects with the exhaust pipe I35 to convey exhausting fluid to the reservoir 38.

It will be readily apparent from the foregoing disclosure that each time the reversing lever 46 is shifted at the ends of the table: stroke, a shifting movement will be imparted to the valve III to shift the reversing valve 91 and thereby impart an oscillatory movement to the motor vane 92 which in turn imparts a corresponding oscillating movement to the feed pawl 69.

It is desirable to provide a readily accessible means for rendering operative either the pilot valve H0 or the pilot valve III. A control knob I55 located on the front of the machine base I9 is mounted on the end of a rotatable shaft I56. The shaft I56 carries a gear I51 (Fig. 6) which meshes with a gear I58 mounted on the nd of a rotatable shaft I59. The shaft I59 is provided with a spiral gear I69 (Fig. 6) which meshes with a spiral gear IEI (Fig. which is fixedly mounted on the left-hand end of the rotor I95 of the selector valve I04. It will be readily apparent from the foregoing disclosure that a slight rotary movement of the knob I55 on the front of the machine base will be imparted to rotate the rotor I05 of the selector valve I94 so as to render operative either the pilot valve I III to provide a continuous infeed of the grinding wheel for a plunge-cut operation or to render operative the pilot valve I I I so that an intermittent infeed ing movement is obtained at the end of the reciprocatory stroke of the table II for a traverse grinding operation.

The operation of this improved feeding mechanism will be readily apparent from the foregoing disclosure. Assuming the parts to have been previously adjusted, a work piece I6 is placed in operative position in the machine and the lever 44 is shifted to start the flow of fluid in a trayerse grinding operation if desired, and the knob I55 is shifted into the traverse grinding position so as to render the pilot valve III operative to control the reversing valve 91 in timed relation with the shifting of the reversing lever 46 to impart an intermittent feeding movement of the grinding wheel at the end of the table stroke. The bolt I1 and sleeve 18 are adjusted relative to the axis of the shaft I4 and crank plate 13 so that the desired oscillating movement will be imparted to the feed pawl 69 at each actuation of the motor vane 92. If a plunge-cut grinding operation is desired, the knob I55 is shifted to render the pilot valve IIO operative so that it controls the shifting movement of the reversing Valve 91. The pilot valve I I0 being automatically shifted by and in timed relation with the oscillating movement of the motor vane 92, will provide an automatic continuous oscillation of the motor vane 92 which in turn will impart a continuous oscillation of the feed pawl 69 in the manner above described to provide a continuous infeeding movement of the grinding wheel for a plunge-cut grinding operation.

The passages I00 and I060, in the rotor I05 of the combined selector and speed control valve I04 serves as throttling means whereby fluid under pressure conveyed to the motor may be varied as desired to vary the speed of the feeding movement of the grinding wheel I! either during a continuous plunge-cut grinding operation or during an intermittent traverse grinding operation.

It will thus be seen that there has been provided by this invention apparatus in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a grinding machine having a longitudinally movable table, a rotatable work support thereon and a transversely movable rotatable grinding wheel, means to reciprocate said work table longitudinally, a wheel feeding mechanism operatively connected to move said wheel transversely, a fluid motor to actuate said feeding mechanism, a reversing valve to change the direction of movement of said motor, a pair of independent pilot valves each operatively connected to shift said reversing valve in either direction, operative connections between the table reciprocating mechanism and one of the pilot valves whereby the reversing valve and the motor may be actuated to produce an infeeding movement of the grinding wheel intermittently at the ends of the table stroke, operative connections between the second pilot valve and the fluid motor whereby the motor actuates the second pilot valve continuously to produce a continuous infeed or plunge-cut, and a selector valve whereby one of the pilot valves may be rendered operative while the other remains inoperative.

2. In a grinding machine having a longitudinally movable rotatable work support and a transversely movable rotatable grinding wheel, means including a reversing lever to reciprocate said work support longitudinally, a wheel feeding mechanism operatively connected to move the grinding wheel transversely, a vane type fluid motor to actuat said feeding mechanism, a reversing valve operatively connected to control the direction of movement of said motor, a pair of independent pilot valves, operative connections between each of the pilot valves and the opposite ends of said reversing valve whereby either of the pilot valves ma be utilized to actuate said reversing valve, operative connections between the table reversing lever and one of said pilot valves whereby the reversing valve and the fluid motor may be actuated intermittently to produce an infeeding movement of the grinding wheel at the ends-of the work table stroke, operative connections between th second pilot valve and the fluid motor vane whereby the motor actuates the second pilot valve continuously to produce a plunge-cut feed of the grinding wheel, and a selector valve whereby either of said pilot valves may be rendered operative to control said motor,

3. In a grinding machine having a longitudinally movable rotatable work support and a transversely movable rotatable grinding wheel, means including a reversing lever to reciprocate said work support longitudinally, a wheel feeding mechanism including a nut and screw operatively connected to move said wheel transversely, a pawl and ratchet to rotate said screw, a vane-type fluid motor to oscillate said pawl, a reversing valve associated with said motor, a pair of independent pilot valves each of which is operatively connected to actuate said reversing valve, operative connections between the table reversing lever and one of said pilot Valves whereby the pilot valve, the reversing valve and the motor may be actuated intermittently at the ends of the table stroke, operative connections between the second pilot valve and the fluid motor vane whereby movement of the motor vane actuates said second pilot valve continuously to operate said motor, and a control valve whereby one of the pilot valves is rendered inoperative while the other is rendered operative.

4. In a grinding machine having a longitudinally movable rotatable work support and a transversely movable rotatable grinding wheel, means including a reversing lever to reciprocate said table longitudinally, a wheel feeding mechanism including a nut and screw operatively connected to move said wheel transversely, a pawl and ratchet to rotate said screw, a vane-type fluid motor including a single rotatable vane to oscillate said pawl, a fluid actuated reversing valve associated with said motor, a pair of independent pilot valves each cf which is connected to the ends of said reversing valve, operative connections between said reversing lever and one of said pilot valves whereby the pilot valve, the reversing valve and the fluid motor may be actuated intermittently to feed the grinding wheel transversely at the ends of the table stroke, operative connections between the second pilot valve and the fluid motor vane whereby the motor actuates the second pilot valve continuously to operate said motor to produce a plunge-cut infeeding movement, and a manually operable selector valve whereby one of the pilot valves is rendered operative while the other pilot valve is rendered inoperative.

5. In a grinding machine having a longitudinally movable rotatable work support and a transversely movable rotatable grinding wheel, a traverse mechanism to reciprocate said work support longitudinally, a wheel feeding mechanism to move said wheel transversely, a fluid motor operatively connected to actuate said feeding mechanism, a reversing valve associated with said motor, a pair of independent pilot valves each operatively connected to actuate said reversing valve, operative connections between the traverse mechanism and one of said pilot valves whereby the motor may be actuated intermittently at the ends of the table stroke, operative connections between the second pilot valve and the fluid motor whereby the motor may be actuated continuously, and a combined selector and speed control valve whereby either of said pilot valves may be rendered operative and whereby the speed of the motor may be varied during either continuous or intermittent operation.

6. In a grinding machine having a longitudinally movable table, a rotatable work support thereon and a transversely movable rotatable grinding wheel, means including a reversing lever to reciprocate said work table longitudinally, a wheel feeding mechanism operatively connected to move said wheel transversely, a fluid motor to actuate said feeding mechanism, a reversing valve to change the direction of movement of said motor, a pair of independent pilot valves each operatively connected to shift said reversing valve in either direction, operative connections between the table reversing lever and one of the pilot valves whereby the motor may be actuated to produce an infeeding movement of the grinding wheel intermittently at the ends of the table stroke, operative connections between the second pilot valve and the fluid motor whereby the motor actuates the second pilot valve continuously to operate said motor to produce a continuous infeed or plunge-cut, and a combined selector and speed control valve whereby either of said pilot valves may be rendered operative and whereby the speed of the motor may be varied during either continuous or intermittent operation.

7. In a grinding machine having a longitudinally movable rotatable work support and a transversely movable rotatable grinding wheel, means including a reversing lever to reciprocate the table longitudinally, a Wheel feeding mechanism including a nut and screw mechanism operatively connected to move said wheel transversely, a pawl and ratchet to rotate said screw, a vane-type motor including a single rotatable vane to oscillate said pawl, a fluid-actuated, shuttle-type reversing valve to control the admission to and exhaust of fluid from said motor, a fluid chamber in each end of said reversing valve, a pair of independent pilot valves each of which is connected to admit fluid under pressure to the end chambers of said reversing valve, operative connections between the reversing lever and one of said pilot valves whereby the fluid motor may be actuated intermittently to feed the grinding wheel transversely at the ends of the table stroke, operative connections whereby rotation of the fluid motor vane serves to actuate the other of said pilot valves so as to feed said wheel continuously for a plunge-cut grinding operation, and a manually operable control valve whereby one of the pilot valves is rendered operative while the other remains inoperative. WALLACE H, WOOD, 

